Updates: April 2017
YouTube Logo
Filter/Buffer

Filter/Buffer - Guitar Synthesizer Processor with Subsonic Filters, Auxiliary Inputs and Master Effects Loop

Features and Specifications:

  • 1 - 13-Pin Roland Guitar Input
  • 1 - 13-Pin Roland Guitar Synthesizer Output
  • 6 - Butterworth 4-pole high pass filters, operating at 50 Hz, 75 Hz, and 100 Hz.
  • 2 - Auxiliary Inputs, high-impedance matched for direct guitar or bass output. Also compatible with any audio source.
  • 1 - Master effects loop input, TRS (tip-ring-sleeve). Effects loop processes both the conventional guitar signal carried by the 13-pin cable, plus the two auxiliary input signals.
  • All-analog processing, no latency added to synthesizer
  • Custom manufactured, high-quality dual layer glass epoxy circuit board
  • Backed by Two-Year Parts and Labor Warranty
  • Power Consumption: 31 mA
  • Size: 130 (W) mm x 105 (H) mm x 34 mm
  • Weight: 11 oz.
  • OUT OF PRODUCTION

Video:


Filter/Buffer - Roland 13-pin Guitar Synthesizer Pre-Processor

The Filter/Buffer does three things: first, the six subsonic filters remove non-musical and mechanical noise from the output of a 13-pin Roland guitar synth controller to improve synthesizer tracking and COSM modeling.

Second, the Filter/Buffer provides two buffered auxiliary inputs to enable non-GK equipped guitars or any audio source to access COSM amp modeling and effects in a Roland guitar synthesizer like the GR-55. Finally, the Filter/Buffer adds a master effects loop for both the two auxiliary inputs, and the normal guitar output from the Roland 13-pin guitar synth controller.

Download the Filter-Buffer Schematic

The schematic for the final revision of the acclaimed Filter/Buffer is available here! Click here to download.

The circuit used 4 quad op-amps, three of the op-amps were used for the filtering circuit, and the last op-amp was used for the buffer. To simplify the design and for quality control 1 uF capacitors are used for all filters, with the values of the resistors changing to set the filter cutoff points.

You will notice that the circuit also includes a +5 volt voltage regulator. This added a +5 volt output to the circuit, which could be used to control the volume of the attached Roland guitar synth. A few acoustic players wanted to be able to control the volume of their synth with a foot pedal, rather than using the GK S-Volume control.

All the parts for building the Filter-Buffer should be readily available, though you may have to purchase from a large distributor such as Mouser Electronics to get the exact value of the resistors required.

Introduction to the Filter/Buffer 13-pin Roland Guitar Synthesizer Processor:

Filter-Buffer

The Filter/Buffer does three things: first, the six subsonic filters remove nonmusical and mechanical noise from the output of a 13-pin Roland guitar synth controller to improve synthesizer tracking and COSM modeling.

Second, the Filter/Buffer provides two buffered auxiliary inputs to enable non-GK equipped guitars or any audio source to access COSM amp modeling and effects in a Roland guitar synthesizer like the GR-55.

Finally, the Filter/Buffer adds a master effects loop for both the two auxiliary inputs, and the normal guitar output from the Roland 13-pin guitar synth controller.

"Finally had a break in the weather and hooked up the filter buffer and gr55. Fantastic! No ghost notes at all, except when I get sloppy. The better I played, the better it sounded. Didn't have to touch the sensitivity adjustment at all. Perfect out of the box. Definitely worth the money. Thanks so much for providing a permanent fix for this problem. - Gus"

History and Development:

The basic idea of the Filter/Buffer is not new, for years Roland included subsonic filtering as a part of the circuit design of the Roland VG-8 and VG-88.

Roland VG-88
Previous Roland synths like the VG-88 included subsonic filtering.

But when the VG-99 shipped in 2007, players with piezo systems like the Godin guitars with the RMC pickups, or the Graphtech Ghost system, immediately noticed that patches that worked so well with the VG-88 were muddy and indistinct on the VG-99. Even after a Roland software update, the problem remained.

Richard McClish, founder of RMC Pickup company, developed a replacement electronics board specifically for the VG-99, the V9SF. The V9SF contained six, Butterworth subsonic filters that restored the subsonic filtering to the VG-99 and solved the problems piezo guitar players were having. Similarly, when the GR-55 shipped in 2011, Richard McClish developed an electronics board for the GR-55, the RMC OPT-01 tracking optimizer.

Now, the Filter/Buffer is the first product of its kind offered as an inline device. Meaning that it can be used with the GR-55 or VG-99. Placing the Filter/Buffer before a Roland US-20, or UX-20 clone, means that both attached synthesizers get the benefit of the filtered guitar signal.

Butterworth Filter
The Butterworth Filter design was selected for the flat response in the passband range.

The Filter/Buffer follows Richard McClish’s published specifications, using 6, 4-pole, -24 DB per octave Butterworth subsonic filters, operating at 50, 75 and 100 hz.

The Butterworth design was chosen for its flat frequency response in the passband range. The filter points were selected to keep musical information, but eliminate mechanical noise that can effect both synthesizer tracking, and COSM modeling.

The Filter/Buffer even benefits Roland GK-3 equipped guitars that may be using a tremolo system, or players that experience problems with palm muting, as this can also add unwanted mechanical noise to the divided hex pickup output.

Auxiliary Inputs and Master Effects Loop - Use Non-GK Guitars to Access COSM Modeling Amp and Effects:

In addition to the benefits of subsonic filtering, the Filter/Buffer has two auxiliary inputs, designed to accommodate the impedance of conventional guitar pickups, but any audio source can be used.

Filter-Buffer Diagram
Filter/Buffer diagram. Click on image to enlarge.

Auxiliary input signals one and two are mixed together, using an active mixing system, and combined with the conventional guitar output from the 13-pin guitar.

Before these blended signals are sent to the attached Roland synthesizer, they also pass through a master effects loop.

The master effects loop enables a chain of effects pedal to be used with both the 13-pin Roland guitar synth controller, and with the auxiliary inputs.

In the video clips shown below, both a bass and keyboard are used with the FIlter/Buffer, and a Roland EV-5 is used in the effects loop as a master volume control.

Links to more information:

Photos:

Filter Buffer Filter Buffer Filter Buffer
Filter Buffer Filter Buffer Filter Buffer
Filter Buffer Filter Buffer Filter Buffer
Filter Buffer Filter Buffer Filter Buffer
Click on any image for larger view.

More Videos:


Filter/Buffer - Roland 13-pin Guitar Synthesizer Processor with Subsonic Filters, Auxiliary Inputs and Effects Loop - Performance Video

The Filter/Buffer used with the Roland GR-55, a Fernandes Dragonfly GK-3 equipped guitar, Venom synth and vintage Roland G-77 Bass.

The factory Patch 30-1 was used for most of the clip, since the patch is set up to incorporate the normal guitar signal. At the end, I switch to the 01-3 GR-300 solo patch.


Filter/Buffer - Roland 13-pin Guitar Synthesizer Processor with Subsonic Filters, Auxiliary Inputs and Effects Loop - Boss GP-10

The Filter/Buffer is a guitar synthesizer preprocessor specifically designed to condition the signals from piezo equipped guitars to maximize their operation with Roland and Boss guitar synths.

This video outlines the benefits of using the Filter/Buffer with the Boss GP-10 guitar processor..

Frequently Asked Questions:

  • Does the Filter/Buffer add any latency or delay?

  • No. None of my processors add any delay at all. Like the GR-300 and GR-100, they are purely analog processors that do not suffer from the inevitable latency introduced by digital systems.

  • Will the Filter/Buffer work with ANY Roland Guitar Controller or Guitar Synth?

  • I have tested the Filter/Buffer with the Roland GK-3, and the Godin LGX-SA guitar using the RMC pickup system. The Filter/Buffer has also been successfully tested with the Roland GR-55 and VG-99.

  • Does this unit require any power?

  • No. The Filter/Buffer gets its power from the connection to the guitar synthesizer. This is the same approach Roland used for the BC-13, US-20 and GKP-4.

  • What guitar benefits most from the Filter/Buffer?

  • In my personal experience, hollow body guitars, like acoustic guitars such as the Godin ACS-SA series, or semi-hollowbody guitars, like a ES-335, benefit the most. These guitars seem to transmit more low frequency energy in the body of the guitar. I owned an Xotica EA-1 with the Graphtech Ghost system, and the GR-300 emulation in the VG-99 was just about unusable without additional subsonic filters.

  • What effects does Filter/Buffer enable non-GK equipped guitars to access in the GR-55?

  • The Filter/Buffer provides access to the Amplifier COSM modeling section, which includes parameters such as amplifier type (Fender Twin, Matchless, Marshall, Mesa/Boogie, etc.), tone controls, speaker type (1x8", 4x10" etc.), speaker microphone type (Shure SM57, AKG, Neuman, etc.), microphone distance, position, and microphone level.

    The Amplifier COSM modeling section is followed by the MOD section, which includes popular guitar effects like Overdrive, Wah, Compression or Octave. The Filter/Buffer also provides access to the MultiFX section. The MFX section has Roland effects from common (equalizer, phaser) to more esoteric effects such as Super Filter (switchable -12, -24 or -36 dB per octave filtering), Step Phaser, Slicer, and Lofi Compression.

    Finally, there is a global effects section with Chorus, Delay, Reverb, and Master 4 band equalizer, with hi and low shelving filters, and two sweepable mid-band filters. The Filter/Buffer input signals can also be looped using the GR-55 phrase looper, as shown in this video.

  • Does the Filter/Buffer enable non-GK equipped guitars to access synthesizer sounds in the GR-55?

  • No. If you want to trigger piano sounds, or play the modeled Roland GR-300 analog synth, you will still need a divided hex pickup, like the Roland GK-3 or similar.

  • Does the Filter/Buffer effect the sound of the guitar?

  • No. Check out the video demo. The Filter/Buffer only removes subsonic, nonmusical information. For example, the direct sound of the piezo pickups, unprocessed, is exactly the same, with and without the Filter/Buffer. If you are playing a GK-3 equipped guitar, the Filter/Buffer will not change the sound of your guitar in any way, but you will still have the benefits of the additional Auxiliary Inputs, and the Master Effects Loop.

  • I bought the external Filter/Buffer for the GR 55. I can not get this to work. I tried running an auxiliary guitar with no GK-3 pickup into the aux 1 input on the Filter/Buffer and the output goes to 13-pin GK Input. I don't hear any sound.

  • The fastest way to test the Filter/Buffer with the GR-55 is to call up factory Patch LEAD 30-1. Not all the factory presets allow the normal guitar input to be heard, but LEAD 30-1, 30-2, and 30-3 all use the normal guitar signal. I used LEAD 30-1 in the demo video, and everything Filter/Buffer is tested with this patch to insure the unit is properly functioning before it ships.